1. Field of the Invention
This invention relates to a method for production of tin-cobalt, tin-nickel, or tin-lead binary alloy electroplating bath composition and an electroplating bath produced thereby which produces a tin-cobalt, tin-nickel, or tin-lead binary alloy coating glossy and excellent in decorative effect and permits stable plating work.
2. Prior Art Statement
Methods for electrodepositing tin-cobalt, tin-nickel, and tin-lead binary alloy platings have been known in the art.
A method disclosed by T. L. Ramachar "Electrochemistry", 25, 573 (1957), a method disclosed by A. E. Davies and R. M. Angleo "Trans. Inst. Metal Finishing", 33, 277 (1956), and a method disclosed by A. Brenner "Electrodeposition of alloys", vol. 2, 339 (1963) are examples. The coatings electrodeposited in a large thickness by these known methods have a disadvantage that they have no gloss, assume a grayish white color, and sustain cracks under strong stress.
For this reason, these alloy coatings can be used only for thin decorative coatings, though they possess as high corrosion proofness as Monel Metal or Inconel.
As tin-lead alloy electrodepositing baths, a borofluoride bath, a pyrophosphoric acid bath, etc. are available. These methods have problems relating to the safety of workers and are apt to cause water pollution. Moreover, the bath compositions are susceptible to degeneration due to oxidation because they use divalent tin.
The inventors continued a study with a view to developing a plating method which is free form the drawbacks of such conventional methods as described above and is capable of producing a glossy coating without reference to thickness. So far they have secured Japanese Patent No. 1,027,262 for an invention characterized by containing 1-hydroxyethane-1,1-phosporic ester or a salt thereof in a plating bath, Japanese Patent No. 1,027,292 for an invention characterized by further containing aldehyde and a betaine compound, and Japanese Patent No. 1,166,434 and No. 1,180,236 for an invention characterized by containing glycol ether.